Well not so much disillusionment as disappointment…maybe?
One of my favorite games is Fallout 3 and then Fallout: New Vegas, both worlds are large and visually interesting (well somewhat) but story wise, nothing grabs me. Even the usual stellar B plots are just uninteresting.
Contrast that Metro 2033, both the novel and the game. They have an intense dark atmosphere and a rich interesting world. All the little stations have a personality to them, you can taste Artyom’s fear in places. The game replicates it quite well, within it’s confines.
And it seems that Metro’s author making the story as an allegory to modern Russia is what does it. Realising that the story has more then one level is fantastic. But Fallout never reaches that.
But I play to poke my head in holes and shoot things.